Ultra-wide direct band gap semiconductors hold great promise for deep ultraviolet opto-electronic applications. Here we evaluate the potential of MgSiN2-GaN alloys for this purpose. Although MgSiN2 itself has an indirect gap ∼0.4 eV below its direct gap of ∼6.5 eV, its different sign lattice mismatch from GaN in two different basal plane directions could avoid the tensile strain which limits AlxGa1−xN on GaN for high x. Two octet-rule preserving structures (with space groups Pmn21 and P1n1) of a 50% alloy of MgSiN2 and GaN are investigated and are both found to have gaps larger than 4.75 eV using quasiparticle self-consistent (QS) GW calculations. Both are nearly direct gap in the sense that the indirect gap is less than 0.1 eV lower than the direct gap. Their mixing energies are positive yet small, with values of 8 (31) meV/atom for Pmn21 (P1n1) indicating only a small driving force toward phase separation.
@article{arxiv.2208.00908,
title = {Quaternary MgSiN_2-GaN alloy semiconductors for deep UV applications},
author = {Ozan Dernek and Walter R. L. Lambrecht},
journal= {arXiv preprint arXiv:2208.00908},
year = {2022}
}